Index and table drive means for a machine tool

ABSTRACT

A single drive and control means is selectively engageable to provide either rectilinear movement to the table base or rotary movement of an index table carried by the table base.

BACKGROUND OF THE INVENTION

The present invention relates to a single drive and control means forproviding rectilinear movement to a table base and rotary movement to anindex table of a machine tool, selectively.

Prior to this invention, the inclusion of an index table in the tablebase of a machine tool added greatly to the mechanical complexity andcost of the machine tool. This was due to the necessity of providing aseparate driving means for both the supporting table base and the indextable, which necessitated duplicating the numerous flexible couplings,fittings, hoses, wires, and the like required to energize and controlthe separate driving means for the index table and the separate drivingmeans for the movable table base.

SUMMARY OF THE INVENTION

It is, therefore, the object of the present invention to provide asimple, inexpensive means for providing rectilinear motion to a tablebase and rotary motion to the index table of a machine tool through theoperation of a single drive and control means.

According to the present invention, there is provided to a machine toolhaving a bed supporting a table base for rectilinear movement along thebed. The table base includes at least one index table carried therebyand rotatably indexable about its own axis and relative to the tablebase on which it is supported. A single means comprising a common drive,a control means and a coupling means operable to engage the drive andcontrol means to operate either the table base or index tableselectively.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a machine tool incorporating thefeatures of the present invention;

FIG. 2 is a fragmentary, enlarged view in vertical section through thetable base and supporting bed, taken in a plane along the lines 2--2 ofFIG. 1 and showing table 34 in the stationary or nonmovable position andtable 34A in the rotating position;

FIG. 3 is an end view of the table base showing the relationship of theinput drive shafts for effecting X-axis movement of the table base androtary motion of the index table.

FIG. 4 is a developed view of the drive mechanisms taken in the planerepresented by the line 4--4 in FIG. 3.

FIG. 5 is an enlarged fragmentary side view of the checker valve andalso showing the engagement of the shifting fork to the ring gear of theshiftable gear mechanism.

FIGS. 6 and 6A are diagrammatic views of the hydraulic circuit depictingthe various positions of an index table.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring now to FIG. 1, there is shown therein a machine tool of thetype with which the present invention may be employed. Machine tool 10includes a bed 12 which supports a vertical column 13. The verticalcolumn 13 contains a pair of ways 14 on which is mounted a saddle 16,for vertical movement along the Y-axis relative to the column. Saddle 16includes a second set of ways 17 on which is mounted for horizontalmovement along the Z-axis, a spindle head 18. Spindle head 18 contains atool spindle 20 in which is inserted metal working tool 21. Tool spindle20 is rotated by motor 22.

Machine tool bed 12 is provided with a pair of longitudinal ways 23,which support a table base 24 for horizontal movement along the X-axisin front of column 13 and spindle head 18.

A lead screw 26 engages a nonrotatable nut (not shown) in spindle head18 and moves spindle head 18 along the Z-axis of the machine tool whenthe former is rotated. The lead screw may be rotated by any suitablemeans such as the electric motor 27. A rotary signal generator 28, whichmay be of the photoelectric or electromagnetic type, is affixed toelectric motor 27 to provide a series of pulses or signals correspondingto the rotation of the electric motor 27 to an automatic control means30. Electric motor 27 and the other motors employed in machine tool 10may be energized and regulated by the automatic control means 30connected to the machine tool 10 by conduit 31. The automatic controlmeans 30 includes a tape reader 32 which reads recorded data on punchedtape 33 in a well-known manner to provide the operating control signalsto the machine tool.

FIG. 2 shows an embodiment of the present invention in which the tablebase 24 is provided with a pair of index tables 34 and 34A. Theinclusion of such a pair of index tables is desirable to permit theworkpiece on one of the tables to be machined while the previouslymachined workpiece on the other index table is removed and a newworkpiece is affixed to the table. Table base 24 is then moved orshuttled so that the new workpiece undergoes the machining operationwhile the previously machined workpiece is removed.

The index tables are each rotatably movable on the table base 24 abouttheir own axis which extends through the table base and parallel to ways14 and the Y-axis of machine tool 10 so that the workpiece may berotated on the table base without the necessity of unclamping andreclamping the workpiece to the table base. Such rotary motion of theindex tables is in addition to the relative motion of table base 24 andspindle head 18.

As shown in FIG. 2, the table base 24 is slidably mounted on ways 23 andmoved along the ways by a lead screw 38 extending through nut 39, whichis secured to the machine bed 12. Lead screw 38 is rotated in eitherdirection by an electric motor 40, shown in FIG. 1, which is provided ina well-known manner with a rotary signal generator 42 to provide aseries of pulses or signals corresponding to the number of rotations ofmotor 40.

The construction and operation of table 34A is the same as 34, so thefollowing description of table 34 will apply to table 34A.

Index table 34 includes the flat disc portion 43 containing T slots 36.A column 44 extends downwardly from disc 43 along the axis of rotationof index table 34. Index table 34 is journaled in a collar 45 by meansof an upper bearing 46 and a lower bearing 47. Collar 45 is, in turn,fitted in a sleeve 48 for axial movement in the sleeve. Such axialmovement permits the raising and lowering of the index table 34 withrespect to table base 24. Sleeve 48 is secured to a circular web member53 formed in the table base 24 by means of screws 49.

Index table 34 is prevented from moving when it is in its lowermostposition by operation of a toothed coupling 50. The toothed coupling 50is formed of a pair of rings 51 and 52 having engaging teeth projectingfrom the opposing annular planes of the rings. When the teeth areengaged, as shown by table 34, relative rotary motion between rings 51and 52 is prevented. When the teeth are disengaged, as by raising ring51A, as shown by the position of table 34A, relative rotation betweenthe two rings is permitted.

Ring 51 is mounted on the underside of disc 43 of index table 34 withits teeth extending downwardly so as to engage the upwardly extendingteeth of ring 52 mounted on sleeve 48.

The toothed coupling 50 also provides a means for accurately controllingthe positioning of index table 34. For this purpose, the number of teethcut in the rings corresponds to the minimum indexing increment desired.For example, if it is desired to index table 34 every 5° of arc, 72teeth are cut into each of the rings 51 and 52. Thus, teeth may be fullyengaged only every 5° of rotation of index table 34 and accurateindexing of the table into these 5° increments is insured.

The periperal surface 55 of index table 34 contains a limit switchactuator 56 which actuates limit switches 57 and 58 in a mannerhereinafter described.

Index table 34 is indexed or rotatably moved by a motion translatingmeans interposed between the table base 24 and the index table 34. Suchmotion translating means includes a ring gear 60 which is secured to theunderside of the disc portion 43 of the table 34 adjacent the toothedcoupling 50. Table base 24 has an idler gear assemblage 62 disposedbetween the two index tables 34 and 34A. A carrier 61 is secured to theweb members 53 and 53A of the table base 24 by screws 63. The carrier 61is provided with three in-line circular openings in which shafts 64, 68and 72 are rotatably supported. To this end shaft 64 is supported in thecentral opening in carrier 61 by bearings 65 and 66; shaft 68 issupported in the lefthand opening, as viewed in FIG. 2, by bearings 69and 70; and shaft 72 is supported in the right-hand opening, as viewedin FIG. 2, by bearings 73 and 74. A spur gear 75 is mounted on the upperend of shaft 64 so as to engage both a gear 77, which is mounted onshaft 68, and a gear 78, which is mounted on shaft 72. A ring gear 80 ismounted on the lower end of shaft 64 so as to engage with a gear 81which is secured on a reduced inner end portion of a horizontal indexdrive shaft 85. Index drive shaft 85 is rotatably supported at itsrightward end by bearing 89 and 90 located in a support block 86, whichis secured by screws 93 to the bottom of carrier 61, as illustrated inFIG. 2. The left end of shaft 85 is rotatably supported in bearings 91and 92, as shown in FIG. 4, located in the gear drive box 41. A drivingsleeve 95 is secured to shaft 85 by a key 96. Mounted on the right endof sleeve 95 is an index table drive gear 98 and mounted on the left endof sleeve 95 is an index locking gear 99.

In normal operation, when rotary movement of index tables 34 or 34A isnot desired, the index tables remain in the lowered position as depictedby the position of index table 34 in FIG. 2. Under this condition theindex table drive shaft 85 is disconnected from motor 40 by a shiftablegear assembly 84 which will hereinafter be described. When motor 40 isdisconnected from index table drive shaft 85, it is connected to drivethe X-axis screw 38 and thereby move table base to the desired X-axisposition. At this time shaft 85 and the idler gear assemblage 62 do notrotate while machine tool 10 is in its nonindexing mode of operation.This results in a more favorable torque to inertia ratio for the X-axisdrive motor 40. This also results in less wear in the mechanical partsof the index drive because the index drive is engaged only during theactual indexing movements of the tables 34 and 34A.

X-axis drive screw 38 is rotatably supported by a bearing 87 located inend surface 83 of the table base 24, as shown in FIG. 2, and a bearing88 carried in a gear drive box 41, as shown in FIG. 4, which is securedto the outer surface of the table base 24 located at the other end ofthe table base 24. An X-axis drive gear 102 is secured to the left endof screw 38 by a key 101. The output shaft 103 of the DC drive motor 40is provided with a ring gear 104 which is keyed thereto.

The shiftable gear assembly 84, as shown in FIGS. 4 and 5, is providedwith a locking plate 107 having an extending tubular sleeve portion 108.The locking plate 107 is provided with internal splines (not shown)which are slidably engaged with complementary splines 110 that areformed on shaft 112. Shaft 112 is fixedly secured in the gear drive box41. A gear 114 is carried for rotation relative to locking plate 107 onthe outer races of a pair of bearings 115 and 116. The bearings 115 and116, in turn, are mounted on the extending sleeve portion 108 of thelocking plate 107. Therefore, gear 114 is free to rotate while thelocking plate 107, coupled by its spindles (not shown) with thecomplementary splines 110 of stationary shaft 112, remains in itsangular fixed position. Ring gear 114 is always in mesh with motoroutput gear 104 so as to transmit power from the DC motor 40 to eitherthe X-axis drive gear 102 or the index table drive gear 98, selectively.

A shifting fork 124 is used to effect the axial movement of theshiftable gear assembly 84 from its leftward position, as viewed in FIG.5, where the shiftable gear assembly is engaged with the X-axis drivegear 102, to its rightward position where the shiftable gear assembly 84is engaged with the index drive gear 98. The shifting fork 124 issecured to an actuating rod 126 of a hydraulic actuator assembly 128.The bifurcated extending end 125 of the shifting fork 24 engages eitherside of the index locking plate 107. Thus, when the hydraulic actuatorassembly 128 is actuated, the shifting fork 124 will move the shiftablegear assembly 84 axially along shaft 112 in one direction or the other.

FIGS. 4 and 5 show the actuating rod 126 biased to the left which, inturn, effects the engagement of the gear 114, of shiftable gear assembly84, with the X-axis drive gear 102. When the actuating rod 126 is biasedto the right, this will effect the engagement of gear 114 with the indextable drive gear 98. Since the output gear 104 of DC motor 40 is alwaysengaged with gear 114 of the shiftable gear assembly 84, the poweroutput of motor 40 will be used to drive either the X-axis screw 38 orthe index drive shaft 85, selectively.

As shown in FIG. 5, the hydraulic actuator assembly 128 for effectingthe selective drive engagement of the X-axis screw 38 or the index tabledrive shaft 85 with the motor 40 is comprised of a valve body 130 havingthree axial bores 131, 135 and 136. The valve body 130 is secured to theexternal surface of the gear drive box 41 with screws 132. The outer orleftward end of axial bores 135 and 136 are closed by an end cap 138which is secured with screws 139 to the outer end of valve body 130. Theactuating rod 126 extends outwardly from the shifting fork 124 through asuitable opening 141 of gear box 41 and through the axial bore 131 andoutwardly through an opening 140 of the outer end cap 138.

Slidably carried within the axial bores 135 and 136 are valve spools 147and 148 respectively. Axial bores 135 and 136 in cooperation with thevalve spools 147 and 148 respectively, form checker valve assemblies 150and 151, respectively. Checker valves 150 and 151 regulate the raisingand lowering of the index tables 34 and 34A, respectively. Theconstruction and operation of checker valve 151 is the same as checkervalve 150, so that the description of the construction and operation ofthe checker valve 150 will apply to checker valve 151. Axial bore 135 isdivided by the spool 147 into three subchambers 135A, 135B and 135C.There are five ports, 165, 166, 167, 168 and 169 provided whichcommunicate with the axial bore 135 of the checker valve assembly 150.Selective admission of hydraulic fluid into the axial bore 135 via theseports control the position of valve spool 147 and consequently thevertical movement of the index table 34.

As shown in FIG. 5, the leftwardly extending portion 153 of spool 147,passes through a ore 154 formed in the end closure cap 138. Secured onthe extreme leftward end of spool portion 153 is a collar 156. A sleeve158 having a flange portion 159 is secured to actuating rod 126 so thatthey move axially in unison. Sleeve 158 is carried for axial slidablemovement in an enlarged diameter portion 160 of the bore 131. Thearrangement is such that an inner surface 162 of collar 156 abuts asurface 163 of flange 159. Therefore, as checker valve 150 is actuatedto effect the movement of spool 147 to the right, as viewed in FIG. 5,the engagement of collar 156 with flange 159 will effect the rightwardmovement of actuating rod 126. The rightward movement of actuating rod126 will effect the movement of the gear 114 of the shiftable gearmember assembly 105, out of engagement with the X-axis drive gear 102and into engagement with the index table drive gear 98.

As shown in FIGS. 4 and 5, the actuating rod 126 is depicted in itsextreme leftward position, which is the position it is in when theshifting fork 124 has effected the movement of the shiftable gearassembly 84 into engagement with the X-axis drive gear 102. Thus, theoutput of the common drive motor 40 is transmitted to the X-axis drivescrew, via ring gear 114 and drive gear 102, to effect the rectilinearmovement of the table base in one direction or the other, depending uponthe rotation of motor 40.

When it is desired to connect the output of the common drive motor 40 tothe index table drive gear 98 for effecting indexable movement of eithertable 34 or 34A, hydraulic pressure fluid will be supplied through port165, into subchamber 135A to exert a force on spool surface 171 to movethe spool 147 rightwardly as viewed in FIG. 5. As spool 147 moves to theright, hydraulic fluid in subchamber 135B will be drained through port166 to an oil reservoir 181, as shown in FIG. 6. The rightward movementof spool 147 will effect the shifting of ring gear 114 from engagementwith the X-axis drive gear 102 into meshing engagement with the indextable drive gear 98, to effect the rotation of index drive shaft 85 inone direction or the other, depending upon the rotation of motor 40.This is true because as the spool 147 moves to the right, its attachedcollar 156 will engage flange 159 of actuating rod 126 to effect theaxial movement of shifting fork 124 and the shiftable gear assembly 84which is connected to the bifurcated end 125 of shifting fork 124.

When it is desired to disconnect the output of the common drive motor 40from the index drive gear 98 and connect the output of the motor 40 tothe X-axis drive gear 102, hydraulic pressure fluid will be suppliedthrough port 167 to subchamber 135C, to apply a force to spool surfaces173 and 174. As hydraulic pressure fluid is supplied to subchamber 135Cit will flow through passage 175 formed in valve body 130 to supplypressure fluid to a chamber 177 formed by the bore 143 and the inner endof sleeve 158. The hydraulic pressure fluid in chamber 177 applies aforce to end surface 178 of sleeve 158. Since the combined surface areasof surfaces 173 and 178 is greater than the area of surface 174, adifferential force will be exerted to effect the leftward movement ofpiston rod 126. The leftward movement of piston rod 126 will effectleftward movement of the shifting fork 124, thereby shifting the sleeve108 to reconnect the ring gear 114 with the X-axis drive gear 102.

The hydraulic circuit for driving the various components described isillustrated diagrammatically in FIGS. 6 and 6A and comprises a pump 180connected to draw hydraulic fluid from the reservoir 181. The output ofthe pump 180 is discharged into a pressure line 182 with the exhaustfluid being carried back to the reservoir by return line 183.

Index table 34 is raised from the position shown in FIG. 6 to theposition depicted in FIG. 6A by energizing solenoid 184 to actuate valve185 to connect pressure line 182 to port 165 of checker valve 150. Thehydraulic pressure fluid will pass through port 165 into subchamber 145Aand exert a force on spool surface 171 to effect the rightward movementof spool 147 as viewed in FIG. 5. When spool surface 171 moves past port168, hydraulic pressure fluid will flow out of port 168 and into annularchamber 189 of table base 24 via fluid conduit 188, as shown in FIG. 2.The hydraulic pressure fluid admitted to annular chamber 189 acts on aradial flange 194 of the collar 45 to effect upward movement of thecollar, thereby elevating the index table 34. As the index table 34 iselevated, hydraulic pressure fluid will be exhausted from a chamber 193located above radial flange 194, via fluid conduit 191 through port 169of checker valve assembly 150. The fluid entering subchamber 135B viaport 169 will pass out of drain port 166 to the reservoir 181. Also, asthe spool 147 is moved to the right, the hydraulic fluid withinsubchamber 135C will exhaust through internal passage 195 formed withinthe spool 147 to subchamber 135B and, consequently, it will also exhaustthrough exhaust port 166 to return to reservoir 181.

As a prerequisite to the indexing of table 34, to rotatably position theworkpiece, table base 24 has to be located along ways 23 at any 0.01inch position. The positioning of table base 24 at any 0.01 inchposition, along the X-axis will insure the meshing of the index lockingplate 107 with the X-axis drive gear 102 and consequently it will insurethe meshing of ring gear 114 with the index table drive gear 98 and themeshing of index table ring gear 60 with gear 77 of the idler gearassembly 62. If a wrong X-axis distance is called for, for example onenot at a 0.01 inch position, such as 20.022, the teeth of locking gear107 and the teeth of the drive gear 102 will not be in position tomeshingly engage and, therefore, gears will hang up. This will preventthe actuating rod 126 from moving all the way to the right and,therefore, will not allow spool 147 to move all the way to the rightand, therefore, port 168 will be blocked and pressure fluid enteringport 165 will not be supplied to chamber 189 and consequently the indextable 34 will remain in its lower position as depicted in FIG. 6.Consequently the index table will not rise and the X-axis positioncalled for will have to be checked and corrected so that a 0.01 positionis commanded.

When the shiftable gear assembly is shifted between the two drive gears98 and 102 it is desirable to keep a fixed angular relationship betweenthe rotor of the signal generator 42, which is connected to motor 40,and the two drive gears 98 and 102. To this end the locking plate 107 isused to angularly lock one of the drive gears 98 or 102 before itdisengages the other.

As depicted in FIG. 4, the lower portion locking plate 107 is in meshwith the index locking plate 99 when the actuating rod 126 is in itsleftward position. As the actuating rod 126 is moved to the right, itwill be noted that the upper portion of locking plate 107 will engageand lock the X-axis drive gear 102 in its angular position before thelower portion of locking plate becomes disengaged from the index lockingplate 99. When the shiftable gear assembly 84 is in its far rightposition, ring gear 114 is in driving engagement with the index tabledrive gear 98. When the leftward movement of the shiftable gear assembly84 is effected by the movement of actuating rod 126, it will be notedthat the lower section of locking plate 107 will engage and lock theindex plate 99 in its angular position before the ring gear 114 becomesdisengaged with the index table drive gear 98. Therefore the interactionof locking plate 107 with the X-axis drive gear 102 and with the indexlocking plate 99 will insure that the signal generator 42 will be in afixed angular relation with both the X-axis drive gear 102 and the indextable drive gear 98.

The index table 34 is lowered into table base 24 by deenergizingsolenoid 184, valve 185 will be spring returned to the position shown inFIG. 6, to connect the pressure line 182 to port 167 of checker valve150. Hydraulic fluid will pass through subchamber 145C and out of port169 to fluid conduit 191 which is connected to annular chamber 193. Thepressure fluid acting on the upper surface of the radial flange 194 willforce the index table 34 downwardly. As the index table 34 is moveddownwardly, the hydraulic fluid below radial flange 194 in annularchamber 189 is exhausted through conduit 188 to port 168 of checkervalve 150. The hydraulic fluid entering chamber 135B will pass throughdrain port 166 to reservoir 181.

For example, let it be assumed that the index table 34 has been stoppedat the 20.000 X-axis position and that the index table has beenelevated. When the index table 34 is fully elevated, limit switch 57 isactuated and operates to allow the DC motor 40 to drive the index table34. The X-axis signal generator 42 is driven by motor 40 and is utilizedto control the rotation of the index table 34. To this end, gear ratiosare used so that one revolution of the signal generator 42 is equal toone degree of index table movement. When the motor 40 is connected tothe X-axis drive screw 38, gear ratios are used so that one revolutionof the signal generator 42 is equal to 0.1 inch of X-axis travel. If wedesire to rotate the now elevated index table 34, 20°, the signalgenerator 42 would have to be driven by motor 40 through 20 revolutions.One revolution of signal generator 42 equaling 1° of index tablemovement. To this end, the tape 33 would call for a new X-axis positionof 22.000 inches. A new X-axis distance of 2.000 inches effects twentyrevolutions of signal generator 42 since one tenth of an inch of X-axistravel called for by the tape 33 effects one revolution of signalgenerator 42.

After the necessary rotation, the index table 34 will be lowered. Whenthe table is all the way down, limit switch 58 is actuated whichoperates to effect the next block of tape to be read. This is amiscellaneous function which counts the "X" position register back towhere it started at the start of the index cycle. It is not necessary tomove the signal generator 42, since the signal generator is in the sameposition as it was when it started the index cycle (20 signal generatorrevolutions will produce 20° of indexing at the table). When moving theaxis position register back, it is done at a faster feed rate than thenormal X-axis feed rate travel, to save time. After the X-axis positionregister is counted back to its original position before the index cyclebegan, the control 30 is now ready to read the next command from theinput tape.

Although the illustrative embodiment of the invention has been describedin considerable detail for the purpose of disclosing a practicaloperative structure whereby the invention may be practicedadvantageously, it is to be understood that the particular apparatusdescribed is intended to be illustrative only and that the novelcharacteristics of the invention may be incorporated in other structuralforms without departing from the spirit and scope of the invention asdefined in the subjoined claims.

The principles of this invention having now been fully explained inconnection with the foregoing description, we hereby claim as ourinvention:

We claim: .[.
 1. In a machine tool having table base supported forrectilinear movement along a supporting bed, said table base beingprovided with an index table supported by said table base for movementwith it and for independent indexable movement relative to said tablebase;a source of power; a first drive means carried by the bed andoperable to effect the rectilinear movement of said table base; a seconddrive means carried by said table base and operable to effect theindexable movement of said index table; coupling means operable whenactuated to connect said source of power to said first drive means or tosaid second drive means selectively; and control means operable toactuate said coupling means and said power drive means for effectingrectilinear movement of said table or indexing movement of said indextable selectively..]. .[.2. In a machine tool having a bed supporting atable base for rectilinear movement along the bed, at least one indextable carried by said table base and rotatably indexable about its axis;power drive means operably connected to effect either the rectilinearmovement of said table base or the rotary movement of said index table,selectively; a first motion translating means located on said table baseand operably connected to said bed to effect the rectilinear motion ofsaid table base relative to said bed; a second motion translating meanscarried by said table base and operably connected to said index table toeffect the rotary motion of said index table; coupling means operable toengage said power drive means with either said first or second motiontranslating means, selectively; and control means connected to saidpower drive means to regulate the operation of said power drive means;whereby the rectilinear movement of said table base and the rotarymovement of said index table may be selectively effected by operation ofa single power drive..]. .[.3. In a machine tool according to claim 2wherein said first motion translating means includes a screw operablymounted on said table base parallel to the direction of rectilinearmovement of said table base; and, a nut secured to said machine tool bedand operably connected to said screw..]. .[.4. In a machine toolaccording to claim 2 wherein said second motion translating meansincludes a gear secured to said index table in coaxial relationshiptherewith; a gear transmission carried by said table base; means toeffect engagement between said index table gear and said geartransmission; and, a drive shaft connected to receive the input drivefrom said power drive means and transmit it to said geartransmission..]. .[.5. In a machine tool according to claim 4 whereinsaid coupling means includes a shiftable drive transmission operablydisposed to engage said screw or said drive shaft selectively, saidshiftable drive transmission being operably connected to receive thepower input drive from said power drive means..]. .[.6. A machine toolaccording to claim 2 wherein said power drive means includes a motor..]..[.7. A machine tool according to claim 2 wherein said control meansincludes a signal generator operative to provide a signal indicating thenumber of revolutions of said motor; and, a position register connectedto said signal generator and operable to indicate either the amount ofrectilinear distance said table base traveled or the amount of rotationof said index table, selectively..]. .Iadd.
 8. In a machine tool havinga bed supporting a table base for rectilinear movement along the bed, atleast one index table carried by said table base and rotatably indexableabout its axis; a motor; a first motion translating means located onsaid table base and operably connected to said bed to effect therectilinear motion of said table base relative to said bed; a secondmotion translating means carried by said table base and operablyconnected to said index table to effect the rotary motion of said indextable means operable to selectively couple said motor to either saidfirst motion translating means or said second motion translating meansfor actuating said table base in its rectilinear motion or said indextable in its rotary motion selectively; and a single servo control loopfor regulating the operation of said motor to control the movement ofboth of said tables individually so that said single servo control loopautomatically regulates the operation of the longitudinally movabletable in its rectilinear movement alone or the operation of the rotarytable in its rotary movement alone depending upon which of said tablesis being driven at the time. .Iaddend..Iadd.
 9. In a machine toolaccording to claim 8 wherein said first motion translating meansincludes a screw operably mounted on said table base parallel to thedirection of rectilinear movement of said table base; anda nut securedto said machine tool bed and operably connected to said screw..Iaddend..Iadd.
 10. In a machine tool according to claim 8 wherein saidsecond motion translating means includes a gear secured to said indextable in coaxial relationship therewith; a gear transmission carried bysaid table base; coupling means to effect engagement between said indextable gear and said gear transmission; and a drive shaft connected to berotated by said motor and being connected to drive said geartransmission. .Iaddend..Iadd.
 11. In a machine tool according to claim10 wherein said coupling means includes a shiftable drive transmissionoperably disposed to engage said screw or said drive shaft selectively,said shiftable drive transmission being operably connected to receivethe power input drive from said motor. .Iaddend. .Iadd.
 12. A machinetool according to claim 8 wherein said single servo control loopincludes a signal generator operative to provide a signal indicating thenumber of revolutions of said motor; and a position register connectedto said signal generator and operable to indicate either the amount ofrectilinear distance said table base traveled or the amount of rotationof said index table, selectively. .Iaddend.